This invention relates to methods and compositions for bonding a fluoropolymer to a substrate.
Fluorine-containing polymers (also known as xe2x80x9cfluoropolymersxe2x80x9d) are a commercially useful class of materials. Fluoropolymers include, for example, crosslinked fluoroelastomers and semi-crystalline or glassy fluoropolymers. Fluoropolymers are generally of high thermal stability and are particularly useful at high temperatures. They may also exhibit extreme toughness and flexibility at very low temperatures. Many of these fluoropolymers are almost totally insoluble in a wide variety of solvents and are generally chemically resistant. Some have extremely low dielectric loss and high dielectric strength, and may have unique non-adhesive and low friction properties. Fluoroelastomers, particularly the copolymers of vinylidene fluoride with other ethylenically unsaturated halogenated monomers such as hexafluoropropylene, have particular utility in high temperature applications such as seals, gaskets, and linings.
Multi-layer constructions containing a fluoropolymer enjoy wide industrial application. Such constructions find utility, for example, in fuel line hoses and related containers and hoses or gaskets in the chemical processing field. Adhesion between the layers of a multi-layered article may need to meet various performance standards depending on the use of the finished article. However, it is often difficult to establish high bond strengths when one of the layers is a fluoropolymer, in part, because of the non-adhesive qualities of fluoropolymers. Various methods have been proposed to address this problem. One approach is to use an adhesive layer or tie layer between the fluoropolymer layer and the second polymer layer. Surface treatments for the fluoropolymer layer, including the use of powerful reducing agents (e,g., sodium naphthalide) and corona discharge, have also been employed to enhance adhesion. In the case of fluoropolymers containing interpolymerized units derived from vinylidene fluoride, exposure of the fluoropolymer to a dehydrofluorinating agent such as a base has been used, as well as polyamine reagents applied to the fluoropolymer surface or incorporated within the fluoropolymer itself.
A multi-layer structure includes a fluoropolymer bonded to a substrate. The structure is prepared by heating a bonding composition, and optionally under pressure, to form the bond. The bonding composition includes an amino-substituted organosilane. The bonding composition includes non-adhesive materials.
In one aspect, a method of bonding a fluoropolymer to a substrate includes providing a bonding composition between a fluoropolymer and a substrate to form a primed article and heating the primed article to a temperature and optionally applying pressure for a sufficient time to bond the fluoropolymer and the substrate to form a bonded article. The bonding composition includes an amino-substituted organosilane. The primed article may be heated to a temperature between 50 and 300xc2x0 C., preferably between 100 and 250xc2x0 C.
The bonding composition may be provided between the fluoropolymer and the substrate in different ways. For example, a surface of the fluoropolymer may be treated with the bonding composition and the treated surface of the fluoropolymer may be contacted with a surface of the substrate, or a surface of the substrate may be treated with the bonding composition and the treated surface of the substrate may be contacted with a surface of the fluoropolymer. In certain embodiments, a mixture of the fluoropolymer and the bonding composition may be extruded and a surface of the extruded mixture may be contacted with a surface of the substrate. In other embodiments, the substrate or the fluoropolymer may be cast from solution or polymerized from a monomer.
In another aspect, a method of bonding a fluoropolymer to a substrate includes treating a surface of the fluoropolymer with a bonding composition including an amino-substituted organosilane having a hydrolyzable substituent, contacting the treated surface of the fluoropolymer with a surface of a substrate, and heating the contacted surfaces to a temperature for a sufficient time to bond the fluoropolymer and the substrate to form a bonded article.
In yet another aspect, a method of bonding a fluoropolymer to a substrate includes extruding a mixture of a fluoropolymer and a bonding composition including an amino-substituted organosilane having a hydrolyzable substituent, contacting a surface of the extruded mixture with a surface of a substrate, and heating the contacted surfaces to a temperature for a sufficient time to bond the fluoropolymer and the substrate to form a bonded article.
In yet another aspect, a bonded article includes a fluoropolymer having a surface, a substrate having a surface, and a bonding composition interposed between the surface of the fluoropolymer and the surface of the substrate, the bonding composition including an amino-substituted organosilane. In another aspect, a laminated article includes a first layer having a surface and a substrate having a surface in contact with the surface of the first layer, in which the first layer includes a fluoropolymer and a bonding composition including an amino-substituted organosilane. The substrate may include an inorganic substrate, such as a metal or a glass, or an organic substrate, such as a non-fluorinated polymer. The fluoropolymer may include a polymer derived from a monomer selected from the group consisting of a vinylidene fluoride monomer, and ethylene combined with a comonomer, the comonomer being selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, 3-chloropentafluoropropene, a perfluorinated vinyl ether, vinyl fluoride and a fluorine-containing diolefin.
The amino-substituted organosilane may have a hydrolyzable substituent. The amino-substituted organosilane may be 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, (aminoethylaminomethyl)phenethyltrimethoxysilane, (aminoethylaminomethyl)phenethyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltris(2-ethylhexoxy)silane, 6-(aminohexylaminopropyl)trimethoxysilane, 4-aminobutyltrimethoxysilane, 4-aminobutyltriethoxysilane, p-aminophenyltrimethoxysilane, 3-(1-aminopropoxy)-3,3,-dimethyl-1-propenyltrimethoxysilane, 3-aminopropyltris(methoxyethoxyethoxy)silane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, or aminoundecyltrimethoxysilane.
The bonding composition may include a phase transfer catalyst or an acid catalyst. Preferably, the phase transfer catalyst or acid catalyst may be a phosphonium salt, an ammonium salt, a fluoroaliphatic sulfonyl compound, a perfluoroalkylcarboxylic acid, or an arylcarboxylic acid.
The bonding composition may include a solvent to facilitate applying a coating of the composition to a surface of the fluoropolymer or the substrate, or both. The solvent may be removed, for example, by drying, prior to contacting the substrate and fluoropolymer surfaces. Any solvent, if used may be a fluorinated solvent, for example, a fluorinated solvent having at least one fluorinated moiety. Fluorinated solvents may be effective at promoting wetting of the bonding composition onto either substrate. Preferred fluorinated solvents include, for example, hexafluoroxylene, hexafluorobenzene, and the like.
Bonded multi-layer materials may have combined physical and chemical properties possessed by both fluoropolymers and non-fluorinated polymers, resulting in less expensive, well-performing articles. For example, the fluoropolymer component may be used in automotive hose and container constructions, anti-soiling films, low energy surface PSA tapes and coatings for aircraft. The bonding process is a mild photochemical lamination that may promote adhesion between a fluoropolymer and a substrate. The bonding composition may be used to form a composite article having a fluoropolymer cladding on a conductive and lustrous metal to protect it from corrosion, a fluoropolymer cladding on glass fibers to enhance their physical strength and chemical resistance for telecommunication, or a fluoropolymer layer bonded to a hydrocarbon substrate in a multi-layer materials.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.